Update SML-NJ

The existing SML-NJ formula does all sorts of nasty things, like spewing
ML files into lib and polluting bin with hidden dot-folders.

Instead of removing it just yet, making it install into libexec.

If you can improve this formula, go for it, otherwise it might be retracted
in the future.

Formula/smlnj.rb

@@ -6,20 +6,6 @@ class Smlnj <Formula
   md5 '97503a4e749a5e72ff975f3883688105'
   version '110.72'
 
-  def install
-    ENV.deparallelize
-    # smlnj is much easier to build if we do so in the directory where it
-    # will be installed.  Thus, we're moving it to the prefix to be built
-    # there.
-    Dir.chdir '..'
-    prefix.install 'config'
-    Dir.chdir prefix
-    File::open('config/targets', 'w') do |f|
-      f << targets
-    end
-    system 'config/install.sh'
-  end
-
   def targets
 <<-EOS
 request ml-ulex
@@ -38,7 +24,33 @@ request cml-lib
 request mlrisc
 request ckit
 request heap2asm
-
 EOS
   end
+
+  def install
+    ENV.deparallelize
+    # smlnj is much easier to build if we do so in the directory where it
+    # will be installed.  Thus, we're moving it to the prefix to be built
+    # there.
+    Dir.chdir '..'
+    libexec.install 'config'
+    (libexec+'config/targets').write targets
+    Dir.chdir libexec
+    system 'config/install.sh'
+  end
+
+  def caveats
+    <<-EOS.undent
+    This formula spews ML files all over lib, and puts hidden subfolders in bin.
+    Because of this, we've installed it to:
+      #{libexec}
+    and we haven't linked it into #{HOMEBREW_PREFIX}
+
+    You'll need to add:
+      #{libexec}/bin
+    to your PATH.
+
+    Improvements are welcome.
+    EOS
+  end
 end